Fuel control valve

ABSTRACT

A valve arrangement for controlling flow of fuel from a positive-displacement pump to an engine such as a gas turbine, the control being exerted by an electric current which biases a pilot valve to regulate a control pressure. The control pressure and pressure of metered fuel act in opposition on a metering valve so that the pressure of fuel delivered to the engine is determined by the control pressure and thus by the electric current. Metered fuel pressure and pump outlet pressure control a by-pass valve which returns excess fuel to the pump inlet. The entire control arrangement preferably is integrated into a compact assembly.

Mai/tee? States Patent 1 1 Carothers, J r.

[ 51 May 8, 1973 1 FUEL CONTROL VALVE {75] Inventor: Frank S. Carothers,Jr., Anderson,

lnd.

[7 3] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Nov. 24, 1971 21 Appl. No.: 201,741

[52] US. Cl. ..417/300,137/116, 137/117 [51] Int. Cl ..F04b 49/00, G05d11/00 [58] Field of Search ..l37/116, 117; 417/293, 300

[56] References Cited UNITED STATES PATENTS 3,572,365 3/1971 White..l37/l 17 Primary Examiner-Martin P. Schwadron Assistant ExaminerDavid.l. Zobkiw Attorney-Paul Fitzpatrick et a].

[5 7] ABSTRACT A valve arrangement for controlling flow of fuel from apositive'displacement pump to an engine such as a gas turbine, thecontrol being exerted by an electric current which biases a pilot valveto regulate a control pressure. The control pressure and pressure ofmetered fuel act in opposition on a metering valve so that the pressureof fuel delivered to the engine is determined by the control pressureand thus by the electric current. Metered fuel pressure and pump outletpressure control a by-pass valve which returns excess fuel to the pumpinlet. The entire control arrangement preferably is integrated into acompact assembly.

2,937,656 5/1960 Evans et al. .137/ll7 X 3,017,922 l/1962 Peterson..137/1l7 X 4 Claims, 5 Drawing Figures Z?\ CONTROL g :k

1 V L ENGINE PATENTEU MAY 8 ms FUEL FUEL CONTROL VALVE My invention isdirected to means for controlling flow of fluid and more particularly toapparatus by which flow of fuel to a gas turbine or other engine may becontrolled by the magnitude of an electric current.

Most known fuel controls for gas turbine engines are of ahydromechanical or pneumatic type, but there are some control systemswhich involve extensive electrical or electronic devices of the generalnature of analog computers or governing controls to regulate fuel flowto the engine. There must be an interface between the electricalapparatus and a valve which controls flow of fuel to the engine.

My invention is concerned with an improved mechanism for this purpose,specifically one by which a rather small current flowing through asolenoid biases a pilot valve which thus variably regulates a controlpressure, this control pressure in turn setting, through the operationof a metering valve, the pressure of the fuel which is delivered to theengine.

The principal objects of the invention are to improve fuel controlsystems and the like and to provide improved means for controllingpressure or flow of a liquid by the use of an electrical current signal.

The nature of my invention and its advantages will be clear to thoseskilled in the art from the succeeding detailed description of thepreferred embodiment of the invention and the accompanying drawingsthereof.

FIG. 1 is a schematic diagram illustrating the nature of the controlapparatus.

FIG. 2 is a sectional view of an electrically controlled valve assemblytaken on the plane indicated by the line 2-2 in FIG. 5.

FIG. 3 is a partial sectional view of the valve body taken on the planeindicated by the line 3-3 in FIG. 2.

FIG. 4 is a partial sectional view of the valve body taken on the planeindicated by the line 4-4 in FIG. 2.

FIG. 5 is an elevation view with a cover removed and parts cut away.

Referring first to FIG. 1, a liquid fuel is stored in a tank 2 fromwhich it flows through a line 3 to the inlet 4 of a pump 6, indicated asa gear pump. The fuel may be pressurized by a boost pump (notillustrated). Pump 6 discharges through an outlet line 7, a meteringvalve 8, and a fuel outlet line 10 to an engine 11. The control isspecifically designed for an engine of the gas turbine type but, ofcourse, may have other applications.

As illustrated in FIG. 1, a control line 12 supplies the fuel outletpressure to the valve 8, this pressure tending to close the valve. Themetering valve 8 also responds to a regulated pressure line 14, thispressure being derived from the pump through a branch line 15 from thepump outlet 7 and an orifice or restricted conduit 16 connecting lines15 and 14. Line 14 also is con nected to a pressure regulating pilotvalve 18 which may allow fuel to bleed from line 14 into a drain line 19to the pump inlet. Flow through valve 18 creates a pressure drop throughorifice l6 and thus varies the pressure in line 14.

Valve 18 is controlled by a solenoid 20 energized from a suitableelectrical control mechanism 22. This control mechanism may be of anysuitable type. Ordinarily, it will include means for transmitting acurrent to the solenoid which is determinative of the pressure of fuelto besupplied to the engine to run the engine at the desired powerlevel. Thus, this voltage might be basically under control of a footaccelerator pedal in an automotive vehicle, for example. Of course, suchcontrols also ordinarily include means to limit or control fuel toprevent over-temperature or overspeed of the engine and to limit fuelduring acceleration to avoid compressor surge; also to prevent fuel flowfrom dropping below a'minimum for any particular engine operatingcondition to prevent flameout. The details of the control mechanism 22are immaterial to our invention, may take any desired form and,therefore, will not be further described.

The remaining principal element of the control is a by-pass valve 23which acts to regulate the head on the metering valve 8 and to return tothe'pump inlet fuel delivered by the pump in excess of enginerequirements. Valve 23 has an inlet through a branch line 24 from thepump outlet and discharges into a return line 26 to the pump inlet.Valve 23 is biased in the closing direction by fuel outlet pressure inbranch 12 from the fuel outlet line 10. It is biased to open by pressurein a branch line 28 from the pump outlet line 7; thus it responds to thepressure drop across metering valve 8.

The operation of the system will be taken up after a description of thepreferred physical embodiment of the valve assembly.

Referring to FIGS. 2 through 5, the fuel control valve assembly 30comprises a body or valve block 31 and a cover plate 32 fixed to thevalve body. Cover plate 32 and a cover 33 enclosing valve 18 are fixedto the body by screws 34, gaskets 35 and 37 being disposed between thecover plate and the body and cover, respectively. Two stepped bores inthe body perpendicular to the cover plate 32 define two valve cylinders36 and 38, cylinder 36 housing the by-pass valve 23 and cylinder 38 themetering valve 8.

Considering first the metering valve 8, this comprises a seat 39retained in the cylinder 38 by a snap ring and sealed by an O-ring, anda valve poppet 40 engaging the seat under the influence of a lightspring 42. Spring 42 bears against a retainer 43 fixed to the stem ofpoppet 40 and the end of the stem bears against a flexible diaphragm 44lodged against a step in the cylinder 38. The diaphragm may be sealed bya gasket and is clamped against the shoulder by a ring 46 and screws 47.Spring 42 provides a small force (for example, about one pound) biasingthe valve closed. The diaphragm 44 divides the cylinder 38 into twochambers, a chamber 48 pressure in which tends to close the valve 8 anda chamber 50 pressure in which tends to open the valve.

Considering now by-pass valve 23, the cylinder 36 mounts a diaphragm 51supported similarly to diaphragm 44. A poppet 52 engages the diaphragmand an annular seat 53 at one end of the cylinder 36. Valve 23 is biasedto close by a relatively strong compression spring 54 which engages in arecess in cover plate 32. A light spring 55 acts to hold the poppet 52in engagement with diaphragm 51. Diaphragm 51 divides cylinder 36 into achamber 56 in which pressure tends to open the by-pass valve and achamber 58 in which pressure tends to close the valve. Cylinder 36communicates through pump inlet connection 4 with the inlet of pump 6and cylinder 38 communicates with the pump outlet through connection 7.The specific structure is adapted for direct mounting of the valveassembly on the pump, but this is immaterial to the invention heredescribed.

The fuel outlet connection of FIG. 1 is shown in FIG. 2 and the inletconnection 3 from the tank is shown in FIG. 4. Outlet 10 connectsdirectly with chamber 48 and through a drilled control line 12 in thevalve block to the chamber 58. Pump outlet connection 7 is connectedthrough line 28 in the valve body with chamber 56 of the by-pass valve.

Referring to FIG. 4, a drilled passage 59 in the valve block connectstank connection 3 with pump inlet connection 4. A second drilled passage60 intersects passage 59 and extends through the face of the valveblock. Referring to FIG. 3, two intersecting drilled passages 62 and 63lead from pump outlet 7 through a very small drilled orifice 16, about0.02 inch in diameter, into the chamber 50 of the metering valve.Passage 63 is closed beyond the orifice by gasket 35 or by plugging.

The pilot valve assembly 18 is mounted on cover plate 32 and is enclosedby the stamped sheet metal cover 33. The space within the cover 33contains fuel at tank or boost pump pressure which is vented through asmall hole 67 in the cover plate which connects through a slot 68 in theface of the valve body with the drain passage 60, 59. The valve assembly18 includes a frame or housing 70 which is fixed to the cover plate 52by cap screws 71. The housing includes a guide for a valve plunger 72which is biased by the solenoid or coil 20. Plunger 72 cooperates withan annular valve seat disk 74 which is clamped between the housing 70and the cover plate 32. Disk 74 has a central circular hole 75 whichoverlies a hole 76 extending through the cover plate 32 into the chamber50 of the metering valve, thus corresponding in part to the line 14 ofFIG. 1. A very light compression spring 78 (above one-half ounce force)biases the plunger in the direction to open the valve. An armature 79hinged on a post 80 is magnetically attracted by energization ofsolenoid to bias the plunger into engagement with the seat. The seat isof small diameter, about 0.070 inch so that the fuel pressure forceexerted on the plunger 72 is relatively small. The magnetic force onplunger 72 tends to close the regulating valve 18 and opposes pressuretending to escape from the chamber 50 to which it is supplied throughthe orifice 16 by the pump. When the force exerted by the fluid on theplunger is less than that due to the solenoid 20 and spring 78, thevalve closes except for immaterial slight leakage. Whenever the pressureforce exerted on the valve plunger through hole 75 exceeds the forceexerted by the solenoid and spring, the valve opens to bleed fluid outand thus maintain the pressure in chamber 50 at a value which isproportional to the pull exerted by the solenoid. The magnetic structureis such that the displacement of the armature is very slight and forceis substantially directly proportional to current flowing in coil 20.Thus, control of this current by the control device 22 determinespressure in chamber 50. Variations in pump outlet pressure will notaffect this relation. Incidentally, it may be advantageous in some casesto mount the valve assembly so that plunger 72 is vertical to minimizefriction there.

As shown in FIG. 5, the solenoid is energized through a pair of leads 82which extend through an opening 83 in the cover into a correspondingrecess in the valve body. External connections are made by a connector84 fixed in a cylindrical bore 86 in the valve body and sealed by anO-ring.

Screws 87 shown in FIG. 5 additionally hold cover plate 32 to the valvebody, resisting fuel pressure within the valve cylinders.

OPERATION Considering the operation of the valve system, let us assumethat the engine is a gas turbine and that it is beginning to be crankedby a starter, and that the pump 6 is geared to the engine or starter.Fuel will flow from the tank 2 through connection 3, 4 to the pump andfrom the pump through connection 7 to valve 8, which is held closed byspring 42, and through passage 28 to the chamber 56 of valve 23, whichis held closed by spring 54. Pump discharge also flows through passages62, 63 (FIG. 3) and orifice 16 into chamber 50 of metering valve 8. Ifwe assume no current is fed to solenoid 20, regulating valve 18 will beopen and pressure will not build up in chamber 50, the fuel being bledoff through valve 18 and returned to the pump inlet through the drain67, 68, 59 (FIGS. 5 and 4).

As cranking speed increases, the discharge of pump 6 increases andbecomes much more than can be bled through orifice 16. At some pointbefore lightoff, this pressure builds up to a point at which thepressure in chamber 56 overcomes the minimal pressure in chamber 58,causing by-pass valve 23 to open and discharge excess fuel to the pumpinlet. The constants of the by-pass valve are preferably such that thepump outlet pressure is maintained at about 35 psi above fuel pressurein line 10, chamber 48, and chamber 58. Too high a metering head undulyloads the pump, and too low a metering head slows response of themetering valve to transients.

When it is desired to supply fuel to the engine for lightofi', solenoid20 is energized by an appropriate control to close valve 18 and allowpressure to build up in chamber 50. This opens valve 8 and fuel flowsinto chamber 48 and out through connection 10 to the engine. Pressure inchamber 48 tends to close the valve and, because of spring 42, apressure differential of about 1 psi in chamber 50 over chamber 48 isrequired to open the valve. The current flowing through solenoid 20determines the force with which plunger 72 of valve 18 is urged againstthe opening of of the valve and therefore the pressure at which the fuelin chambers 50 and 58 is maintained. The metered fuel pressure is thusmaintained at about one psi below this value and, if it tends to becomeexcessive, will simply increase the rate of bleed from chamber 50 toreduce the pressure and reduce the flow area of valve 8.

This pressure differential of about 35 psi controlled by valve 23provides a constant head across the metering valve 8 in normaloperation. This is exerted over the area of the opening in valve seat39, which is not very considerable. The metering valve is controlledalmost entirely by the pressure in chamber 50 as opposed by the feedbackpressure in chamber 48. During lightoff, acceleration, or normaloperation of the engine, the control 22, responding to whatever factorsare appropriate, determines the current fed to solenoid 20, thereby thepressure in chamber 50, 48 and pressure of fuel fed to the engine. Iffuel flow is excessive or insufficient, as reflected by engine speed orother control factor, this will affect the control to adjust the currentin solenoid as required.

It should be apparent to those skilled in the art from the foregoingthat my invention provides a simple, compact, and reliable mechanism todirect fuel to an engine or other user at a desired variable pressureand to by-pass the excess delivery of the pump.

The detailed description of the preferred embodiment of the inventionfor the purpose of explaining the principles thereof is not to beconsidered as limiting or restricting the invention, since manymodifications may be made by the exercise of skill in the art.

I claim:

1. A fuel supply and control system comprising, in

' combination, a positive-displacement pump having an inlet and anoutlet, a fuel outlet, a pressure-differentialoperated throttling valvecontrolling flow from the pump outlet to the fuel outlet, meansresponsive to fuel outlet pressure biasing the throttling valve toclose, conduit means including an orifice and a variably controllablepressure-regulating pilot valve connecting the pump outlet to the pumpinlet, means responsive to the regulated pressure between the orificeand the pilot valve biasing the throttling valve to open, apressuredifferential-operated pump by-pass valve connected between thepump outlet and the pump inlet, means responsive to fuel outlet pressurebiasing the by-pass valve to close, and means responsive to pump outletpressure biasing the by-pass valve to open, such that fuel outletpressure is a predetermined function of regulated pressure and the pumpoutlet pressure is maintained at a substantially constant differentialabove fuel outlet pressure.

2. A fuel supply and control system comprising in combination, apositive-displacement pump having an inlet and an outlet, a fuel outlet,a pressure-differentialoperated throttling valve controlling flow fromthe pump outlet to the fuel outlet, means responsive to fuel outletpressure biasing the throttling valve to close, conduit means includingan orifice and a variably controllable pressure-regulating pilot valveconnecting the pump outlet to the pump inlet, electric currentresponsive means controlling the pilot valve, means responsive to theregulated pressure between the orifice and the pilot valve biasing thethrottling valve to open, a pressure-differential-operated pump by-passvalve connected between the pump outlet and the pump inlet, meansresponsive to fuel outlet pressure biasing the bypass valve to close,and means responsive to pump outlet pressure biasing the by-pass valveto open, such that fuel outlet pressure is a predetermined function ofthe electric current, and the pump outlet pressure is maintained at asubstantially constant differential above fuel outlet pressure.

3. A fluid flow regulating valve device comprising, in combination, avalve body defining two cylinders, a diaphragm in each cylinder dividingit into two chambers, a valve operated by movement of each diaphragm, aspring biasing each valve to close, an outlet connectable to a user andconnected directly to the valve-closing chambers of both cylinders, aninlet for fluid under pressure connnected through one valve to thevalve-closing chamber of the said one valve and connected direc y to thevalve-opening chamber of the other valve, a by-pass connected by thesaid other valve to a point of low pressure, means including an orificeand a pressure-regulating valve connected between the inlet and theby-pass for developing a variable control pressure, and means supplyingthe control pressure to the valve-opening chamber of the said one valve.

4. A fluid flow regulating valve device comprising, in combination, avalve body defining two cylinders, a diaphragm in each cylinder dividingit into two chambers, a valve operated by movement of each diaphragm, aspring biasing each valve to close, an outlet connectable to a user andconnected directly to the valve-closing chambers of both cylinders, aninlet for fluid under pressure connected through one valve to thevalve-closing chamber of the said one valve and connected directly tothe valve-opening chamber of the other valve, a by-pass connected by thesaid other valve to a point of low pressure, means including an orificeand a pressure-regulating valve connected between the inlet and theby-pass for developing a variable control pressure, and means supplyingthe control pressure to the valve-opening chamber of the said one valve,the pressure-regulating valve including current-responsive means settingthe controlled pressure level.

1. A fuel supply and control system comprising, in combination, apositive-displacement pump having an inlet and an outlet, a fuel outlet,a pressure-differential-operated throttling valve controlling flow fromthe pump outlet to the fuel outlet, means responsive to fuel outletpressure biasing the throttling valve to close, conduit means includingan orifice and a variably controllable pressure-regulating pilot valveconnecting the pump outlet to the pump inlet, means responsive to theregulated pressure between the orifice and the pilot valve biasing thethrottling valve to open, a pressure-differential-operated pump by-passvalve connected between the pUmp outlet and the pump inlet, meansresponsive to fuel outlet pressure biasing the bypass valve to close,and means responsive to pump outlet pressure biasing the by-pass valveto open, such that fuel outlet pressure is a predetermined function ofregulated pressure and the pump outlet pressure is maintained at asubstantially constant differential above fuel outlet pressure.
 2. Afuel supply and control system comprising in combination, apositive-displacement pump having an inlet and an outlet, a fuel outlet,a pressure-differential-operated throttling valve controlling flow fromthe pump outlet to the fuel outlet, means responsive to fuel outletpressure biasing the throttling valve to close, conduit means includingan orifice and a variably controllable pressure-regulating pilot valveconnecting the pump outlet to the pump inlet, electric currentresponsive means controlling the pilot valve, means responsive to theregulated pressure between the orifice and the pilot valve biasing thethrottling valve to open, a pressure-differential-operated pump by-passvalve connected between the pump outlet and the pump inlet, meansresponsive to fuel outlet pressure biasing the by-pass valve to close,and means responsive to pump outlet pressure biasing the by-pass valveto open, such that fuel outlet pressure is a predetermined function ofthe electric current, and the pump outlet pressure is maintained at asubstantially constant differential above fuel outlet pressure.
 3. Afluid flow regulating valve device comprising, in combination, a valvebody defining two cylinders, a diaphragm in each cylinder dividing itinto two chambers, a valve operated by movement of each diaphragm, aspring biasing each valve to close, an outlet connectable to a user andconnected directly to the valve-closing chambers of both cylinders, aninlet for fluid under pressure connnected through one valve to thevalve-closing chamber of the said one valve and connected directly tothe valve-opening chamber of the other valve, a by-pass connected by thesaid other valve to a point of low pressure, means including an orificeand a pressure-regulating valve connected between the inlet and theby-pass for developing a variable control pressure, and means supplyingthe control pressure to the valve-opening chamber of the said one valve.4. A fluid flow regulating valve device comprising, in combination, avalve body defining two cylinders, a diaphragm in each cylinder dividingit into two chambers, a valve operated by movement of each diaphragm, aspring biasing each valve to close, an outlet connectable to a user andconnected directly to the valve-closing chambers of both cylinders, aninlet for fluid under pressure connected through one valve to thevalve-closing chamber of the said one valve and connected directly tothe valve-opening chamber of the other valve, a by-pass connected by thesaid other valve to a point of low pressure, means including an orificeand a pressure-regulating valve connected between the inlet and theby-pass for developing a variable control pressure, and means supplyingthe control pressure to the valve-opening chamber of the said one valve,the pressure-regulating valve including current-responsive means settingthe controlled pressure level.